There is sometimes a need to compact one or more localized plies of composite prepreg on a surface of a composite laminate or ply layup that is considerably larger than the localized plies. For example, in the aircraft industry, local patches of composite plies, sometimes referred to as “doublers”, may be applied to certain areas of large scale subassemblies such as fuselage sections in order to add stiffness, strength or reinforcements for fasteners.
In some cases, it may be most efficient to fabricate the doublers offline and then apply them to the fuselage sections as a kit. However, compacting these doublers to a fuselage section may be difficult because of the substantial force required to achieve the necessary compaction pressures, especially where the doublers are relatively large. For example, a door surround or window belt may require several tons of force that must be reacted against the surface of the structure to achieve proper compaction. A similar problem may exist where it is necessary to compact co-cured stringers on tooling or on surfaces of the structure.
Current solutions for reacting compaction forces are largely mechanical, and may require substantial tooling and equipment to handle the necessary reaction loads. The tooling and related equipment may be relatively heavy and expensive, especially where large scale structures such as wings or fuselage sections are involved.
An alternate method for reacting compaction forces involves sealing a vacuum bag over the entire surface of the structure, however this approach may be time consuming and may not allow other work to be performed in parallel with the vacuum bag compaction process. Moreover, problems may be encountered in holding the doubler or stringer in place during the process of applying the vacuum bag to the structure and drawing a vacuum.
Accordingly, there is a need for a method and related apparatus compacting doublers and other uncured part layups on large scale structures that reduce or eliminate the problems discussed above.